Cons: Lacks included car charger relative to top, same-priced competitor. No Japanese/European tuning modes. Fifth-generation version mounts less than perfectly on bottom of iPod; nano version is better.

After a long period in which virtually every major iPod accessory maker rolled out a new FM transmitter solution - some released two or three - there’s been a cooling off in recent months, as many companies decided that their existing offerings were good enough for now. Not so XtremeMac, which unexpectedly replaced its AirPlay2 (iLounge rating: B/C+) - a $60, boxy little transmitter - with two versions of AirPlay Boost ($50), new and improved transmitters made to fit the shapes of fifth-generation iPods and second-generation iPod nanos. Black and white versions are sold for the full-sized iPod, while black and silver versions are sold for the nano. While not as strong a value for the dollar as Belkin’s TuneFM transmitter (iLounge rating: A-), AirPlay Boost is otherwise a strong rival, with impressive audio quality and generally strong industrial design, especially in the iPod nano version.

The basic feature package is the same in each version of Boost: the face has three membrane-style buttons, a Dock Connector pass-through port for charging on the bottom, and a standard male Dock Connector plug on the top. Most conspicuously, Xtreme has also added a repositionable, unobtrusive antenna to the left side of each AirPlay - the part responsible for the “Boost” name. The suggestion here is that an external antenna provides an FM transmission boost that an internal antenna can’t offer, which isn’t always true, but to the extent that AirPlay Boost now has a rubber-coated, separate antenna rather than one that has to broadcast around a circuit board and a hard plastic casing, it improves upon AirPlay2’s performance for sure.

With only one exception, we really liked Boost’s industrial design. Xtreme’s new enclosure perfectly matches the contours of the black and silver iPod nanos - its silver version is a hint off the nano’s own color, but not problematically so - and the fifth-generation iPod version generally does the same with the larger white and black models. Both represent a major step up in iPod integration from the somewhat awkward AirPlay2, which had its own cool blue LCD screen, but was quickly outdated in design and size because of the invention of on-iPod station tuning. Dropping AirPlay2’s integrated LCD enabled XtremeMac to improve Boost’s shape, power consumption, and usability; its only issue remains the 5G version’s less than completely horizontal alignment with the 5G’s bottom. The nano version fits the nano perfectly, and aligns well enough on a 5G that you might consider this version a better buy for both iPods.

Interacting with Boost is a step or two up from the earlier AirPlay2, and a step down from TuneFM. Since Boost has half the number of buttons found on TuneFM - left, right, and an XtremeMac X-man logo in the center - manual station tuning is as easy as pressing left or right at any time, but you need to learn button press techniques to access and change its three preset stations, stereo and monaural broadcasting modes, and other settings. By contrast, TuneFM provides one-touch access to its four preset stations, but forces you to learn button combinations to access its broadcasting and other settings, such as a way to toggle between international (say, Japanese) and US tuning frequencies, which is missing in Boost. Neither system is ideal, but if you’re a frequent station changer or international traveler, TuneFM is the better option. Perhaps to compensate for the loss of its earlier blue screen, Boost does add one cute touch missing from TuneFM and other competitors: there’s a blue LED light at the top of each model’s antenna, which you can dim or turn off to conserve power.

We liked the light enough to leave it on - though it’s modestly less power efficient, it’s a nice little touch. And if you’re concerned about power consumption, you’ll appreciate the fact that XtremeMac uses a standard iPod connector pass-through port, so you can charge Boost with any Dock Connector-equipped car or home charger while the iPod’s in use. There’s only one issue here: Belkin includes a car charger with every TuneFM, whereas with Boost, you have to buy that separately. That fact - its value relative to its top competitor - is the single biggest knock on AirPlay Boost.

But Boost’s broadcasting performance offers a strong counterpoint. Unlike AirPlay2, which was unable to broadcast on 87.9FM - the most frequently “open” station in the United States - AirPlay Boost tunes all the way from 87.9 to 107.FM, and does a great job in both tuning and broadcasting. Xtreme has developed a manual channel-skipping mechanism that’s as close to perfect as we’ve seen, skipping from 104 to 105 to 106 at a reasonable pace when the button’s held down, or from 104.1 to 104.3 to 104.5 when it’s pressed multiple times.

When it actually arrives on a channel - particularly when it’s in the stronger monaural broadcasting mode - it compares quite favorably to the top-rated TuneFM in virtually all regards. On 87.9, we found that Boost’s signal was at least as low in static as TuneFM’s indoors or outdoors, and at times, it was better, particularly at any great distance from the stereo. TuneFM’s fall off at distances is its major limitation; Boost does fall off, but not as rapidly. On the more challenging test station 103.3FM, Boost did a better job of fighting off existing audio interference, and provided a more listenable, though still not ideal, audio signal. Notably, neither unit suffered from the tell-tale issues with older transmitters - bass or treble distortion. TuneFM’s strengths over Boost are two in number: it puts out a somewhat louder default signal, and can be adjusted by the user to lower or increase its volume relative to the connected iPod.

It’s worth a brief additional note that both versions of Boost allow you to change the side angling of their antennas: in the “standard” position, the antenna sits right next to the iPod’s body, radiating partially through it, while at its maximum, left-most angle, it sits at a 90-degree angle, flat with the unit’s bottom. Thanks to a ratcheting mechanism, you can also lock the antenna into other angles other than pure horizontal or vertical positions. We noticed small performance benefits when the antenna was ratcheted one step off the pure vertical, giving its right side a bit more breathing room relative to the attached iPod; your experience and desire to do this may vary.

Overall, XtremeMac has done an impressive job with AirPlay Boost, developing a portable FM transmitter solution that’s sharp-looking, generally easy to use, and strong on audio performance. Though you don’t get a car charger in the package - the most decided advantage of Belkin’s TuneFM - if you’re really struggling to get clean sound from your iPod and car stereo, AirPlay Boost should be one of the first options you consider.

Editors' Note: iLounge only reviews products in "final" form, but many companies now change their offerings - sometimes several times - after our reviews have been published.
This iLounge article provides more information on this practice, known as revving.